Selective catalytical dehydrochlorination of hydrochlorofluorocarbons

ABSTRACT

A dehydrochlorination process is disclosed. The process involves contacting R f CHClCH 2 Cl with a chromium oxyfluoride catalyst in a reaction zone to produce a product mixture comprising R f CCl═CH 2 , wherein R f  is a perfluorinated alkyl group.

BACKGROUND

1. Field of the Disclosure

This disclosure relates in general to the selective catalyticdehydrochlorination of hydrochlorofluorocarbons (HCFCs) to makehydrochlorofluoroolefins (HCFOs). More specifically, the catalyst is achromium oxyfluoride catalyst.

2. Description of Related Art

Hydrochlorofluoroolefins (HCFOs), having low ozone depletion potentialand low global warming potentials, are regarded as candidates forreplacing saturated CFCs (chlorofluorocarbons) and HCFCs(hydrochlorofluorocarbons). HCFOs can be employed in a wide range ofapplications, including their use as refrigerants, solvents, foamexpansion agents, cleaning agents, aerosol propellants, dielectrics,fire extinguishants and power cycle working fluids. For example,HCFO-1233xf (CF₃CCl═CH₂) can be used as a foam expansion agent, fireextinguishant, refrigerant, et al. HCFO-1233xf is also an intermediatein the production of 2,3,3,3-tetrafluoropropene (HFO-1234yf) which is arefrigerant with zero ozone depletion potential and low global warmingpotential.

BRIEF SUMMARY OF THE DISCLOSURE

The present disclosure provides a dehydrochlorination process. Theprocess comprises contacting R_(f)CHClCH₂Cl with a chromium oxyfluoridecatalyst in a reaction zone to produce a product mixture comprisingR_(f)CCl═CH₂, wherein R_(f) is a perfluorinated alkyl group.

DETAILED DESCRIPTION

The foregoing general description and the following detailed descriptionare exemplary and explanatory only and are not restrictive of theinvention, as defined in the appended claims. Other features andbenefits of any one or more of the embodiments will be apparent from thefollowing detailed description, and from the claims.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

Also, use of “a” or “an” are employed to describe elements andcomponents described herein. This is done merely for convenience and togive a general sense of the scope of the invention. This descriptionshould be read to include one or at least one and the singular alsoincludes the plural unless it is obvious that it is meant otherwise.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of embodiments of the present invention, suitablemethods and materials are described below. All publications, patentapplications, patents, and other references mentioned herein areincorporated by reference in their entirety, unless a particular passageis cited. In case of conflict, the present specification, includingdefinitions, will control. In addition, the materials, methods, andexamples are illustrative only and not intended to be limiting.

When an amount, concentration, or other value or parameter is given aseither a range, preferred range or a list of upper preferable valuesand/or lower preferable values, this is to be understood as specificallydisclosing all ranges formed from any pair of any upper range limit orpreferred value and any lower range limit or preferred value, regardlessof whether ranges are separately disclosed. Where a range of numericalvalues is recited herein, unless otherwise stated, the range is intendedto include the endpoints thereof, and all integers and fractions withinthe range.

The term “dehydrochlorination”, as used herein, means a process duringwhich hydrogen and chlorine on adjacent carbons in a molecule areremoved.

The term “hydrochlorofluoroolefin”, as used herein, means a moleculecontaining hydrogen, carbon, fluorine, chlorine, and at least onecarbon-carbon double bond. Exemplary hydrochlorofluoroolefins in thisdisclosure include HCFO-1233xf.

The term “alkyl”, as used herein, either alone or in compound words suchas “perfluorinated alkyl group”, includes cyclic or acyclic andstraight-chain or branched alkyl groups, such as, methyl, ethyl,n-propyl, i-propyl, or the different isomers thereof.

The term “perfluorinated alkyl group”, as used herein, means an alkylgroup wherein all hydrogens on carbon atoms have been substituted byfluorines. Examples of a perfluorinated alkyl group include —CF₃ and—CF₂CF₃.

The term “a chromium oxyfluoride catalyst” is intended to mean achromium oxyfluoride represented by formula Cr₂O_(x)F_(y) whereinx+y/2=3.

The term “amorphous” is intended to mean that there is no substantialpeak in a X-ray diffraction pattern of the subject solid.

The term “product selectivity to R_(f)CCl═CH₂”, as used herein, meansthe molar percentage of R_(f)CCl═CH₂ obtained in the process compared tothe total molar amounts of all products obtained.

The term “dehydrochlorination selectivity to R_(f)CCl═CH₂”, as usedherein, means the molar percentage of R_(f)CCl═CH₂ based on the totalmolar amount of R_(f)CCl═CH₂ and R_(f)CH═CHCl obtained in thedehydrochlorination reaction of R_(f)CHClCH₂Cl.

The term “an elevated temperature”, as used herein, means a temperaturehigher than the room temperature.

Disclosed is a dehydrochlorination process comprising contactingR_(f)CHClCH₂Cl with a chromium oxyfluoride catalyst in a reaction zoneto produce a product mixture comprising R_(f)CCl═CH₂, wherein R_(f) is aperfluorinated alkyl group.

In some embodiments of this invention, R_(f) is —CF₃ or —CF₂CF₃. In someembodiments of this invention, R_(f)CHClCH₂Cl is CF₃CHClCH₂Cl(HCFC-243db), and R_(f)CCl═CH₂ is CF₃CCl═CH₂ (HCFO-1233xf).

Some hydrochlorofluoroolefins of this disclosure, e.g., CF₃CH═CHCl(HCFO-1233zd), exist as different configurational isomers orstereoisomers. When the specific isomer is not designated, the presentdisclosure is intended to include all single configurational isomers,single stereoisomers, or any combination thereof. For instance,HCFO-1233zd is meant to represent the E-isomer, Z-isomer, or anycombination or mixture of both isomers in any ratio.

The starting materials for the dehydrochlorination processes in thisdisclosure, i.e., R_(f)CHClCH₂Cl, can be synthesized by methods known inthe art. For example, HCFC-243db may be prepared by chlorinatingCF₃CH═CH₂ or by the addition reaction of CF₂═CHCl with CFClH₂.

The dehydrochlorination process can be carried out in liquid phase orvapor phase using well-known chemical engineering practice, whichincludes continuous, semi-continuous or batch operations. Thetemperature in the reaction zone is typically from about 200° C. toabout 500° C. In some embodiments of this invention, the temperature inthe reaction zone is from about 275° C. to about 450° C. Thedehydrochlorination process can be conducted at superatmospheric,atmospheric, or subatmospheric pressures. The contact time of thestarting material R_(f)CHClCH₂Cl with the catalyst can be largelyvaried. Typically, the contact time is from about 5 seconds to about 150seconds. In some embodiments of this invention, the contact time is fromabout 10 seconds to about 100 seconds.

The contacting step of this invention may be carried out by methodsknown in the art. In some embodiments of this invention, startingmaterial R_(f)CHClCH₂Cl, optionally with an inert gas and/or HF, is fedto a reactor containing the catalyst. In some embodiments of thisinvention, starting material R_(f)CHClCH₂Cl, optionally with an inertgas and/or HF, is passed through the catalyst bed in a reactor. In someembodiments of this invention, starting material R_(f)CHClCH₂Cl,optionally together with an inert gas and/or HF, may be mixed with thecatalyst in a reactor with stir or agitation.

Optionally, the dehydrochlorination process may be conducted in thepresence of HF. In some embodiments of this invention, HF is co-fed intothe reactor with the starting material. In some embodiments of thisinvention, the mole ratio of HF to the starting material R_(f)CHClCH₂Clin the reaction zone is from about 0.1:1 to about 50:1. In someembodiments of this invention, the mole ratio of HF to the startingmaterial R_(f)CHClCH₂Cl in the reaction zone is from about 5:1 to about25:1. In some embodiments of this invention, the mole ratio of HF to thestarting material R_(f)CHClCH₂Cl in the reaction zone is no more than0.9. In some embodiments of this invention, the mole ratio of HF to thestarting material R_(f)CHClCH₂Cl in the reaction zone is no more than0.5. In some embodiments of this invention, the mole ratio of HF to thestarting material R_(f)CHClCH₂Cl in the reaction zone is no more than0.1.

Optionally, the dehydrochlorination process may also be conducted in thepresence of an inert gas such as He, Ar, or N₂. In some embodiments ofthis invention, the inert gas is co-fed into the reactor with thestarting material.

It was found through experiments that chromium oxyfluoride catalysts aresuitable for selective dehydrochlorination process of this disclosure.

The chromium oxyfluoride catalysts can be made by treating Cr₂O₃ withHF, CCl₃F, COF₂ or hydrofluorocarbons. In one embodiment of thisinvention, a chromium oxyfluoride catalyst is made by treating dry Cr₂O₃with a fluorination agent such as CCl₃F or HF. This treatment can beaccomplished by placing the Cr₂O₃ in a suitable container (which can bethe reactor to be used to perform the subsequent selective catalyticdehydrochlorination reaction) and thereafter passing HF over the dryCr₂O₃ for a suitable period of time (e.g., about 15 to about 800minutes) at a suitable temperature (e.g., about 200° C. to about 450°C.), such as what described in Example 1.

In another embodiment of this invention, a chromium oxyfluoride catalystis made by treating Cr₂O₃ with a hydrofluorocarbon at an elevatedtemperature.

Cr₂O₃ is commercially available from BASF Catalysts LLC, 25 MiddlesexEssex Turnpike, Iselin, N.J. 08830-0770.

Cr₂O₃ can also be prepared by reducing chromium (VI) oxide in water witha suitable reducing agent, such as ethanol, as disclosed in U.S. Pat.No. 3,258,500. Of note is the so-called gel-type activated Cr₂O₃obtained by reducing chromium trioxide (CrO₃) and dehydrating thereduced product in the manner disclosed by Ruthruff in “InorganicSynthesis”, Vol. II, pp. 190-193, published in 1946 by McGraw-Hill BookCo., N.Y., and by Turkevich and Ruthruff in U.S. Pat. No. 2,271,356. Inone embodiment of this invention, Cr₂O₃ is prepared by dissolvingchromium trioxide in water, gradually adding ethanol or other suitablereducing agent to the solution and heating under reflux conditions untilthe Cr₂O₃ gel precipitates, separating the gel from the reactionmixture, drying it, and then dehydrating and activating the product byheating it at a temperature of from about 400° C. to about 600° C. in aninert atmosphere until the water is removed and an anhydrous product isobtained.

Cr₂O₃ can also be prepared by pyrolysis of ammonium dichromate((NH₄)₂Cr₂O₇) as disclosed in U.S. Pat. No. 5,036,036. Of note is Cr₂O₃prepared by pyrolysing ammonium dichromate and treating (e.g., washingwith deionized water) the resulting Cr₂O₃ to reduce the alkali metalcontent to 100 ppm or less. Also of note is Cr₂O₃ prepared by firsttreating ammonium dichromate containing 60-2000 ppm alkali metal toreduce its alkali metal content to less than 60 ppm and then pyrolysingthe resulting ammonium dichromate with reduced alkali metal content toform Cr₂O₃ containing 100 ppm or less of alkali metal content.

Cr₂O₃ can also be prepared by the reaction of chromium (VI) oxide with areducing solvent, such as methanol, as disclosed in U.S. Pat. No.4,828,818.

The amount of potassium and other alkali metals in Cr₂O₃ can be reducedby a water washing step as disclosed in U.S. Pat. No. 5,036,036. In someembodiments of this invention, the water washing step includes forming aslurry containing 5-15 wt % Cr₂O₃ and deionized water. Stirring of thiswater slurry can be carried out at 35° C. to 65° C. for at least onehour, and in some embodiments for two or more hours. The solids are thenrecovered by filtration, suitably on a plate and frame filter press. Thefilter cake can be analyzed for alkali metal content. The washing stepcan be repeated to obtain a desired level of alkali metal content.

In one embodiment of this invention, the chromium oxyfluoride catalysthas surface area of from about 10 m²/g to about 800 m²/g.

In another embodiment of this invention, the chromium oxyfluoridecatalyst has surface area of from about 20 m²/g to about 400 m²/g.

In another embodiment of this invention, the chromium oxyfluoridecatalyst has surface area of from about 40 m²/g to about 300 m²/g.

In one embodiment of this invention, the chromium oxyfluoride catalystcontains an alkali metal content of about 2000 ppm or less.

In another embodiment of this invention, the chromium oxyfluoridecatalyst contains an alkali metal content of about 300 ppm or less.

In another embodiment of this invention, the chromium oxyfluoridecatalyst contains an alkali metal content of about 100 ppm or less.

In one embodiment of this invention, the chromium oxyfluoride catalystis amorphous.

In another embodiment of this invention, the chromium oxyfluoridecatalyst is prepared from crystalline α-Cr₂O₃.

The form of the catalyst is not critical and may be used as pellets,powders or granules.

The effluent from the reaction zone typically includes residual startingmaterials R_(f)CHClCH₂Cl, desired hydrochlorofluoroolefin productR_(f)CCl═CH₂, dehydrochlorination byproduct R_(f)CH═CHCl and some otherbyproducts. The desired product R_(f)CCl═CH₂ may be recovered from theproduct mixture by conventional methods. In some embodiments of thisinvention, product R_(f)CCl═CH₂ may be purified or recovered bydistillation.

It was found through experiments that the catalytic dehydrochlorinationprocesses of this disclosure produced desired products with highselectivity. In some embodiments of this invention, the productselectivity to R_(f)CCl═CH₂ is at least 90 mole %. In some embodimentsof this invention, the product selectivity to R_(f)CCl═CH₂ is at least95 mole %.

It was also found through experiments that the dehydrochlorinationreaction of this disclosure is highly selective. The dehydrochlorinationreaction of R_(f)CHClCH₂Cl may generate both isomers R_(f)CCl═CH₂ andR_(f)CH═CHCl. It was found that the dehydrochlorination processes ofthis disclosure generate substantially more R_(f)CCl═CH₂ thanR_(f)CH═CHCl. In some embodiments of this invention, thedehydrochlorination selectivity to R_(f)CCl═CH₂ is at least 95 mole % Insome embodiments of this invention, the dehydrochlorination selectivityto R_(f)CCl═CH₂ is at least 99 mole %.

The reactors, distillation columns, and their associated feed lines,effluent lines, and associated units used in applying the processes ofembodiments of this invention may be constructed of materials resistantto corrosion. Typical materials of construction include Teflon™ andglass. Typical materials of construction also include stainless steels,in particular of the austenitic type, the well-known high nickel alloys,such as Monel™ nickel-copper alloys, Hastelloy™ nickel-based alloys and,Inconel™ nickel-chromium alloys, and copper-clad steel.

Many aspects and embodiments have been described above and are merelyexemplary and not limiting. After reading this specification, skilledartisans appreciate that other aspects and embodiments are possiblewithout departing from the scope of the invention.

EXAMPLES

The concepts described herein will be further described in the followingexamples, which do not limit the scope of the invention described in theclaims.

Example 1

Example 1 demonstrates that contacting HCFC-243db with a chromiumoxyfluoride catalyst generates HCFO-1233xf.

Preparation of the Chromium Oxyfluoride Catalyst

6 cc (cubic centimeter) (8.97 gm) of α-chromium oxide were crushed andsieved to 12/20 mesh and filled into an Inconel™ reactor tube (0.43 inchID) to form a catalyst bed, and were treated with HF according to thefollowing procedure. The α-chromium oxide was heated to 400° C. for twohours under a flow of nitrogen of 37.5 sccm (standard cubic centimetersper minute). At the same flow rate of nitrogen, the temperature waslowered to 300° C. for 80 minutes. While at 300° C., the nitrogen flowwas lowered to 26.5 sccm and the HF flow was started at 9 sccm. Whilemaintaining these flows, the temperature was raised to 325° C. for 80minutes, 350° C. for 80 minutes, 375° C. for 200 minutes, 400° C. for 40minutes, and 425° C. for 55 minutes. While maintaining the temperatureat 425° C., the flow of nitrogen was lowered to 18.8 sccm and the HFraised to 15 sccm for 25 minutes. The flow of nitrogen was then loweredto 11.3 sccm, and the flow of HF was raised to 21 sccm for 30 minutes.The flow of nitrogen was then lowered to 3.8 sccm, and the flow of HFwas raised to 27 sccm for 30 minutes. Then nitrogen flow was shut offand the HF flow was raised to 30 sccm for 160 minutes. Afterwards the HFflow was discontinued, and the nitrogen flow was raised to 20 sccm whilecooling the reactor tube temperature to ambient.

Dehydrochlorination Reaction

The reactor tube temperature was then raised to the desired temperature,and HCFC-243db was fed into the reactor tube together with N₂ andoptionally HF as shown in Table 1 below. Products were analyzed by GC-MSand tabulated as mole percentage. The remaining percentages were unknownbyproducts.

TABLE 1 Prod Prod Prod DHC Conv Sel Sel Sel Sel Temp 243db N₂ HF C TMole % Mole % Mole % Mole % Mole % ° C. sccm sccm sccm sec 243db 1233xf1234yf 1233zd 1233xf 297 1.82 2.34 21.55 14 100% 95% 1.9%  0.9% 99 3532.52 2.34 20.57 14 100% 92% 3.7%  1.8% 98 351 2.52 2.34 20.57 14 100%92% 3.7%  1.9% 98 348 2.1 2.34 21.19 14 100% 92% 3.7%  1.8% 98 348 2.12.34 21.19 14 100% 91% 3.8%  1.8% 98 352 1.82 2.34 21.57 14 100% 91%4.2%  1.7% 98 346 1.82 2.34 21.57 14 100% 91% 3.8%  1.6% 98 398 2.522.14 20.58 14 100% 88% 5.7%  2.9% 97 400 2.1 2.14 21.14 14 100% 84% 7.3% 3.2% 96 401 2.1 2.14 21.16 14 100% 87% 6.1%  2.7% 97 397 1.82 2.1421.50 14 100% 87% 6.3%  2.3% 97 400 1.82 2.23 21.50 14 100% 80% 6.8% 2.1% 97 299 2.55 2.59 0 70  97% 92% 0.9%  2.1% 98 300 2.55 2.59 0 70 53% 88% 0.6%  2.5% 97 302 2.1 2.49 0 78  61% 86% 0.6%  2.5% 97 297 2.12.49 0 78  51% 84% 0.6%  2.6% 97 303 1.82 2.39 0 85  54% 81% 0.6%  2.6%97 302 1.82 2.39 0 85  50% 82% 0.6%  2.7% 97 352 2.52 2.39 0 73  95% 78%1.4%  4.2% 95 349 2.52 2.39 0 73  60% 75% 1.1%  4.5% 94 350 2.1 2.39 080  78% 73% 1.3%  4.5% 94 350 2.1 2.39 0 80  62% 71% 1.3%  4.8% 94 3511.82 2.39 0 85  62% 71% 1.4%  4.9% 94 348 1.82 2.39 0 85  55% 70% 1.5% 5.1% 93 401 2.52 2.39 0 73  91% 62% 4.4% 10.5% 86 401 2.52 2.39 0 73 62% 60% 4.7% 12.3% 83 401 2.1 2.39 0 80  78% 54% 5.4% 14.0% 79 399 2.12.39 0 80  66% 54% 6.4% 15.8% 77 400 1.82 2.39 0 85  68% 50% 7.0% 16.6%75 397 1.82 2.29 0 87  60% 49% 8.0% 17.9% 73 Note: Temp = Temperature; CT = Contact Time; Conv = Conversion; Sel = Selectivity; Prod = Product;DHC = Dehydrochlorination; 243db = HCFC-243db; 1233xf = HCFO-1233xf;1234yf = HCFO-1234yf; 1233zd = HCFO-1233zd.

Note that not all of the activities described above in the generaldescription or the examples are required, that a portion of a specificactivity may not be required, and that one or more further activitiesmay be performed in addition to those described. Still further, theorder in which activities are listed are not necessarily the order inwhich they are performed.

In the foregoing specification, the concepts have been described withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the invention as set forth in theclaims below. Accordingly, the specification is to be regarded in anillustrative rather than a restrictive sense, and all such modificationsare intended to be included within the scope of invention.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any feature(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature of any or all the claims.

It is to be appreciated that certain features are, for clarity,described herein in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures that are, for brevity, described in the context of a singleembodiment, may also be provided separately or in any subcombination.

1. A dehydrochlorination process comprising contacting R_(f)CHClCH₂Clwith a chromium oxyfluoride catalyst in a reaction zone to produce aproduct mixture comprising R_(f)CCl═CH₂, wherein R_(f) is aperfluorinated alkyl group.
 2. The dehydrochlorination process of claim1 wherein the dehydrochlorination process is conducted in the presenceof HF.
 3. The dehydrochlorination process of claim 1 wherein the moleratio of HF to R_(f)CHClCH₂Cl in the reaction zone is no more than 0.9.4. The dehydrochlorination process of claim 1 wherein R_(f) is CF₃. 5.The dehydrochlorination process of claim 1 wherein the temperature inthe reaction zone is from about 200° C. to about 500° C.
 6. Thedehydrochlorination process of claim 5 wherein the temperature in thereaction zone is from about 275° C. to about 450° C.
 7. Thedehydrochlorination process of claim 1 wherein the product selectivityto R_(f)CCl═CH₂ is at least 90 mole %.
 8. The dehydrochlorinationprocess of claim 1 wherein the dehydrochlorination selectivity toR_(f)CCl═CH₂ is at least 95 mole %.